The present invention relates to a liquid cooled mold for continuous casting of slab ingots, having wide sides and narrow sides, wherein the wide sides of the mold project beyond the narrow sides in direction of casting.
Continuous casting of slab ingots requires that the ingot be well supported, particularly where the still liquidous core exerts ferrostatic pressure onto the growing skin. Support is more critical the higher a casting speed has been chosen. The usual arrangement for this purpose includes solid wall molds, particularly in the surface level of steel in the mold. Such a mold is about 500 to 1200 mm long (about 20 to about 50 inches). A frame with support rolls is usually provided under the mold to support the withdrawn ingot. It is also known to use adjustable rolls under the narrow sides of the mold for additionally supporting the ingot (see e.g. U.S. Pat. No. 2,284,503).
A solid wall for a mold provides primarily for positive shaping of the ingot-to-be, right in the casting and surface level of the mold. The ingot is supported until the skin is sufficiently thick and capable of load bearing while being self supporting at least to some extent. It should be noted, that too long a mold while seemingly advantageous from the standpoint of providing support, produces considerable friction for the extraction and withdrawal of the ingot from the mold, which friction increases down with distance from the surface level. Eventually friction may become so great that the skin may be damaged and ruptures. Moreover, one has to consider that some shrinkage of the ingot occurs in the lower portion of the mold which, on the one hand, may lead to separation of the ingot skin from the narrow sides of the mold while, on the other hand, the ingot may expand on the wide sides due to creepage of the skin on the narrow sides by operation of the ferrostatic pressure.
Ingot shrinkage is usually compensated by, in a general way, conicity of the mold, i.e. by having the narrow sides slightly inclined towards each other. That, however, may result in a disadvantage; the expansion as produced under ferrostatic pressure may wear the narrow mold sides to an increasing extent in the lower portion of the mold. Furthermore any forcing of the narrow sides of the ingot against the mold sides occurs more or less at random so that heat is transferred from the ingot into the mold sides in a rather nonuniform, even outright inaffectual manner.